Copy the console= kernel arguments from the original system

usr/share/rear/conf/default.conf

@@ -3289,39 +3289,90 @@ SIMPLIFY_TEAMING=no
 
 ####
 # Serial console support for the ReaR rescue/recovery system:
-# By default serial consoles get enabled if serial devices are found and
-# then matching kernel command line parameters like 'console=ttyS0,9600 console=ttyS1,9600'
-# are set when booting the rescue/recovery system (see KERNEL_CMDLINE above).
 # IA64 platforms require it and people need it when no VGA console is available.
-# Specify 'yes' or 'no' or leave it empty to use ReaR's automatism:
+# By default there is serial console support in the ReaR recovery system
+# when 'getty' or 'agetty' and 'stty' can be found,
+# otherwise USE_SERIAL_CONSOLE is automatically set to 'no'.
+# When 'getty' or 'agetty' and 'stty' can be found
+# and there is a 'console=...' option in /proc/cmdline,
+# then USE_SERIAL_CONSOLE is automatically set to 'yes'.
+# With USE_SERIAL_CONSOLE="no" no serial console gets set up,
+# neither for the recovery system kernel nor for the recovery system bootloader.
+# With USE_SERIAL_CONSOLE="yes" plus appropriate SERIAL_CONSOLE_DEVICE... settings
+# serial consoles can be specified for the recovery system kernel and bootloader
+# for example when there is no 'console=...' option in /proc/cmdline
+# or when serial consoles for the recovery system kernel and bootloader
+# should differ from what 'console=...' options in /proc/cmdline tell.
+# By default (when empty) the automatism further described below is used:
 USE_SERIAL_CONSOLE=
-# If you do not want to use all serial devices found as console you can specify the ones to use
-# e.g. SERIAL_CONSOLE_DEVICES="/dev/ttyS0 /dev/ttyS1" provided USE_SERIAL_CONSOLE is turned on.
-# By default (when empty) all serial devices found are used:
+#
+# Devices to be used in general for serial console setup
+# unless explicitly specified via SERIAL_CONSOLE_DEVICES_KERNEL
+# or SERIAL_CONSOLE_DEVICE_SYSLINUX or SERIAL_CONSOLE_DEVICE_GRUB:
+# E.g. SERIAL_CONSOLE_DEVICES="/dev/ttyS0 /dev/ttyS1"
 SERIAL_CONSOLE_DEVICES=
-# Serial consoles for the kernel of the recovery system:
+#
+# Serial consoles for the kernel of the recovery system
+# provided USE_SERIAL_CONSOLE is not 'no':
 # SERIAL_CONSOLE_DEVICES_KERNEL can be device nodes like "/dev/ttyS0 /dev/ttyS1"
 # or 'console=...' kernel parameters like "console=ttyS1,9600 console=tty0" or both like
 # SERIAL_CONSOLE_DEVICES_KERNEL="/dev/ttyS0 console=ttyS1,9600 console=tty0"
-# provided USE_SERIAL_CONSOLE is turned on.
-# By default (when empty) the SERIAL_CONSOLE_DEVICES are used for the kernel:
+# When SERIAL_CONSOLE_DEVICES_KERNEL is empty but SERIAL_CONSOLE_DEVICES is specified
+# then the specified SERIAL_CONSOLE_DEVICES are used for the kernel.
+# By default (when SERIAL_CONSOLE_DEVICES_KERNEL and SERIAL_CONSOLE_DEVICES are empty)
+# serial consoles get enabled for the recovery system kernel via COPY_KERNEL_PARAMETERS
+# for all 'console=...' options that are found in /proc/cmdline.
 SERIAL_CONSOLE_DEVICES_KERNEL=
-# Serial console for SYSLINUX/EXTLINUX when it is used as bootloader for the recovery system:
+#
+# Serial console for SYSLINUX/EXTLINUX when it is used as bootloader for the recovery system
+# provided USE_SERIAL_CONSOLE is 'yes' (automatically with 'console=...' in /proc/cmdline):
 # SYSLINUX supports only one serial device (because the last SYSLINUX 'serial' directive wins).
 # The right /dev/ttyS* can be specified like SERIAL_CONSOLE_DEVICE_SYSLINUX="/dev/ttyS0"
 # or a whole SYSLINUX 'serial' directive can be specified e.g. for /dev/ttyS1 like
 # SERIAL_CONSOLE_DEVICE_SYSLINUX="serial 1 9600"
-# provided USE_SERIAL_CONSOLE is turned on.
-# By default (when empty) the first one of SERIAL_CONSOLE_DEVICES is used for SYSLINUX:
+# When SERIAL_CONSOLE_DEVICE_SYSLINUX is empty but SERIAL_CONSOLE_DEVICES is specified
+# then the first one of SERIAL_CONSOLE_DEVICES is used for SYSLINUX.
+# By default (when SERIAL_CONSOLE_DEVICE_SYSLINUX and SERIAL_CONSOLE_DEVICES are empty)
+# the devices of the 'console=...' options in /proc/cmdline
+# that exist as /dev/ttyS* or /dev/hvsi* character device nodes are used
+# (which excludes /dev/tty0 when there is 'console=tty0' in /proc/cmdline).
 SERIAL_CONSOLE_DEVICE_SYSLINUX=
-# Serial console for GRUB when it is used as bootloader for the recovery system:
+#
+# Serial console for GRUB when it is used as bootloader for the recovery system
+# provided USE_SERIAL_CONSOLE is 'yes' (automatically with 'console=...' in /proc/cmdline):
 # GRUB supports only one serial device (because the last GRUB 'serial' command wins).
 # The right /dev/ttyS* can be specified like SERIAL_CONSOLE_DEVICE_GRUB="/dev/ttyS0"
 # or a whole GRUB 'serial' command can be specified e.g. for /dev/ttyS1 like
 # SERIAL_CONSOLE_DEVICE_GRUB="serial --unit=1 --speed=9600"
-# provided USE_SERIAL_CONSOLE is turned on.
-# By default (when empty) the first one of SERIAL_CONSOLE_DEVICES is used for GRUB:
+# When SERIAL_CONSOLE_DEVICE_GRUB is empty but SERIAL_CONSOLE_DEVICES is specified
+# then the first one of SERIAL_CONSOLE_DEVICES is used for GRUB.
+# By default (when SERIAL_CONSOLE_DEVICE_GRUB and SERIAL_CONSOLE_DEVICES are empty)
+# the devices of the 'console=...' options in /proc/cmdline
+# that exist as /dev/ttyS* or /dev/hvsi* character device nodes are used
+# (which excludes /dev/tty0 when there is 'console=tty0' in /proc/cmdline).
 SERIAL_CONSOLE_DEVICE_GRUB=
+#
+# Examples
+# (provided USE_SERIAL_CONSOLE is not 'no'
+# and 'getty' or 'agetty' and 'stty' can be found):
+#
+# Default behaviour
+# when there is no 'console=...' option in /proc/cmdline
+# then no serial console is set up for the recovery system.
+#
+# Default behaviour when there are for example
+# 'console=ttyS0,9600' and 'console=tty0' in /proc/cmdline
+# then 'console=ttyS0,9600' and 'console=tty0'
+# are used for the recovery system kernel
+# and only /dev/ttyS0 is used as serial console
+# for the recovery system bootloader (SYSLINUX or GRUB).
+#
+# On a headless machine without VGA card but with serial device /dev/ttyS0
+# the kernel would choose /dev/ttyS0 as its console automatically
+# so no 'console=...' kernel option needs to be used and then the automatism described above
+# would not set up a console for the recovery system (in particular not for the bootloader).
+# In this case USE_SERIAL_CONSOLE="yes" and appropriate SERIAL_CONSOLE_DEVICE... settings
+# are needed to manually specify the right console setup for the recovery system.
 ####
 
 ####

usr/share/rear/lib/serial-functions.sh

@@ -6,29 +6,34 @@ function get_serial_console_devices () {
         echo $SERIAL_CONSOLE_DEVICES
         return 0
     fi
-    # Test if there is /dev/ttyS[0-9]* or /dev/hvsi[0-9]*
-    # because when there is neither /dev/ttyS[0-9]* nor /dev/hvsi[0-9]*
-    # the ls command below would become plain 'ls' because of 'nullglob'
-    # cf. "Beware of the emptiness" in https://github.com/rear/rear/wiki/Coding-Style
-    # see https://github.com/rear/rear/issues/2914#issuecomment-1396659184
-    # and return 0 because it is no error when no serial device node exists
-    test "$( echo -n /dev/ttyS[0-9]* /dev/hvsi[0-9]* )" || return 0
-    # Use plain 'sort' which results /dev/ttyS0 /dev/ttyS1 /dev/ttyS10 ... /dev/ttyS19 /dev/ttyS2 /dev/ttyS20 ...
-    # to get at least /dev/ttyS0 and /dev/ttyS1 before the other /dev/ttyS* devices because
-    # we cannot use "sort -V" which would result /dev/ttyS0 /dev/ttyS1 ... /dev/ttyS9 /dev/ttyS10 ...
-    # because in older Linux distributions 'sort' does not support '-V' e.g. SLES10 with GNU coreutils 5.93
-    # (SLES11 with GNU coreutils 8.12 supports 'sort -V') but if 'sort' fails there is no output at all
-    # cf. "Maintain backward compatibility" in https://github.com/rear/rear/wiki/Coding-Style
-    # Furthermore 'sort' results that /dev/hvsi* devices appear before /dev/ttyS* devices
-    # so the create_grub2_serial_entry function in lib/bootloader-functions.sh
-    # which uses by default the first one and skips the rest will result that
-    # the first /dev/hvsi* device becomes used for the GRUB serial console by default
-    # which looks right because /dev/hvsi* devices should exist only on systems
-    # that have the HVSI driver loaded (a console driver for IBM's p5 servers)
-    # cf. https://lwn.net/Articles/98442/
-    # and it seems right that when special console drivers are loaded
-    # then their devices should be preferred by default:
-    ls /dev/ttyS[0-9]* /dev/hvsi[0-9]* | sort
+    # Scan the kernel command line of the currently running original system
+    # for 'console=<device>[,<options>]' settings e.g. 'console=ttyS1,9600n8 ... console=ttyS3 ... console=tty0'
+    # and extract the specified serial device nodes e.g. ttyS1 -> /dev/ttyS1 ... ttyS3 -> /dev/ttyS3
+    local kernel_option console_option_value console_option_device
+    for kernel_option in $( cat /proc/cmdline ) ; do
+        # Continue with next kernel option when the option name (part before leftmost "=") is not 'console':
+        test "${kernel_option%%=*}" = "console" || continue
+        # Get the console option value (part after leftmost "=") e.g. 'ttyS1,9600n8' 'ttyS3' 'tty0'
+        console_option_value="${kernel_option#*=}"
+        # Get the console option device (part before leftmost optional ',' separator) e.g. 'ttyS1' 'ttyS3' 'tty0'
+        console_option_device="${console_option_value%%,*}"
+        # Continue with next kernel option when the current console option device is no serial device (exclude 'tty0').
+        # The special /dev/hvsi* devices should exist only on systems that have the HVSI driver loaded
+        # (a console driver for IBM's p5 servers) cf. https://lwn.net/Articles/98442/
+        [[ $console_option_device == ttyS* ]] || [[ $console_option_device == hvsi* ]] || continue
+        # Test that the matching serial device node e.g. ttyS1 -> /dev/ttyS1 and ttyS3 -> /dev/ttyS3' exists
+        # to avoid that this automated serial console setup may not work in the ReaR recovery system
+        # when serial device nodes get specified for the recovery system that do not exist
+        # in the currently running original system because the default assumption is
+        # that the replacement system has same hardware as the original system,
+        # cf. https://github.com/rear/rear/pull/2749#issuecomment-1196650631
+        # (if needed the user can specify what he wants via SERIAL_CONSOLE_DEVICES, see above):
+        if ! test -c "/dev/$console_option_device" ; then
+            LogPrintError "Found '$kernel_option' in /proc/cmdline but '/dev/$console_option_device' is no character device"
+            continue
+        fi
+        echo /dev/$console_option_device
+    done
 }
 
 # Get the serial device speed for those device nodes that belong to actual serial devices.
@@ -39,64 +44,15 @@ function get_serial_device_speed () {
     # Run it in a subshell so that 'set -o pipefail' does not affect the current shell and
     # it can run in a subshell because the caller of this function only needs its stdout
     # cf. the function get_root_disk_UUID in lib/bootloader-functions.sh
-    # so when stty fails the get_serial_device_speed return code is the stty exit code and not the awk exit code
-    # therefore one can call get_serial_device_speed with error checking for example like
+    # so when stty fails the get_serial_device_speed return code is the stty exit code and not the awk exit code.
+    # Therefore one can call get_serial_device_speed with error checking for example like
     # speed=$( get_serial_device_speed $serial_device ) && COMMAND_WITH_speed || COMMAND_WITHOUT_speed
-    # because the return code of variable=$( PIPE ) is the return code of the pipe,
-    # cf. how get_serial_device_speed is called in cmdline_add_console below.
+    # because the return code of variable=$( PIPE ) is the return code of the pipe
+    # cf. how get_serial_device_speed is called in lib/bootloader-functions.sh
+    # and output/USB/Linux-i386/300_create_extlinux.sh
     # Suppress stty stderr output because for most /dev/ttyS* device nodes the result is
     #   stty: /dev/ttyS...: Input/output error
     # when the device node does not belong to an actual serial device (i.e. to real serial hardware)
     # so get_serial_device_speed is also used to get those device nodes that belong to real serial devices:
     ( set -o pipefail ; stty -F $devnode 2>/dev/null | awk '/^speed / { print $2 }' )
 }
-
-# Add serial console to kernel cmdline:
-function cmdline_add_console {
-    # Nothing to do when using serial console is not wanted:
-    is_true "$USE_SERIAL_CONSOLE" || return 0
-
-    # Strip existing 'console=...' kernel cmd parameters:
-    local param cmdline=""
-    for param in $KERNEL_CMDLINE ; do
-        case "$param" in
-            (console=*) ;;
-            (*) cmdline+=" $param";;
-        esac
-    done
-
-    # Add serial console config to kernel cmd line:
-    local devnode speed=""
-    if test "$SERIAL_CONSOLE_DEVICES_KERNEL" ; then
-        # When the user has specified SERIAL_CONSOLE_DEVICES_KERNEL use only that (no automatisms):
-        for devnode in $SERIAL_CONSOLE_DEVICES_KERNEL ; do
-            # devnode can be a character device node like "/dev/ttyS0" or "/dev/lp0" or "/dev/ttyUSB0"
-            # cf. https://www.kernel.org/doc/html/latest/admin-guide/serial-console.html
-            # or devnode can be a 'console=...' kernel cmd parameter like "console=ttyS1,9600"
-            if test -c "$devnode" ; then
-                if speed=$( get_serial_device_speed $devnode ) ; then
-                    cmdline+=" console=${devnode##/dev/},$speed"
-                else
-                    cmdline+=" console=${devnode##/dev/}"
-                fi
-            else
-                # When devnode is a 'console=...' kernel cmd parameter use it as specified:
-                cmdline+=" $devnode"
-            fi
-        done
-    else
-        local real_consoles=""
-        for devnode in $( get_serial_console_devices ) ; do
-            # Only add for those device nodes that belong to actual serial devices:
-            speed=$( get_serial_device_speed $devnode ) && real_consoles+=" console=${devnode##/dev/},$speed"
-        done
-        cmdline+=" $real_consoles"
-
-        # Add fallback console if no real serial device was found:
-        test "$real_consoles" || cmdline+=" console=tty0"
-    fi
-
-    # Have a trailing space to be on the safe side
-    # so that more kernel cmd parameters could be "just appended" by other scripts:
-    echo "$cmdline "
-}